Devices for the examination of an eye using a Scheimpflug camera offer the possibility for diagnosis of the front chamber of the eye. Basically they offer a special form of the slit lamp examination, whereby the illuminated plane of the eye using a Scheimpflug camera namely has a slit projector, as it can also be used in common slit lamps.
Such slit projectors are known from the state of the art. The principle of the slit projector is based on the refraction media of the front chamber of the eye not being clear but instead thereat, in particular in the shortwave potion of the visible light, occurs a clear scattering. This has the result that a strongly concentrated light beam, namely the projected slit light, which is sent through the optic media of the eye, when viewed laterally, becomes visible in the media, similar to light beams of automobile headlights in fog. The various portions of the refraction media of the eye have a differently strong light scattering capability and can therefore be differentiated. The principle of this focal illumination is perfected in the slit projector. A slit-shaped luminous beam of a high brightness and as high as possible color temperature is being used for the illumination.
The plane in the eye illuminated by means of the slit projector can be photographed by means of a Scheimpflug requirement. A Scheimpflug camera is a camera, which meets the Scheimpflug requirement. The Scheimflug requirement demands that the plane of the object points, this is here the illuminated plane in the eye, the main plane of the camera lens system and the image plane intersect in a common axis. By tilting the image plane relative to the main plane of the camera lens system, it is possible for the object plane to be in any desired special position, whereby object points can be detected in the depth of sharpness zone, which object points at a vertical object plane cannot at the same time be sharply reproduced.
Such a device is known, for example, also from the U.S. Pat. No. 4,171,877. The disadvantage of the device disclosed in this reference is that the voltage supply and also the data transfer occurs by means of cable. Furthermore rotationally fixed parts of the Scheimpflug camera are mounted in such a manner that they lie in the path of rotation of rotatable parts of the Scheimpflug camera. This limits the rotating ability of the Scheimpflug camera and of the slit light projector. This has the disadvantage that a relatively expensive control must be provided for the rotating movement of the Scheimpflug camera and of the slit light projector so that, for example, the cable for the voltage supply or the data transfer are not torn. A multiple scanning of the eye is thus always interrupted by a return of the Scheimpflug camera and of the slit light projector into an initial position. Thus again and again bothersome interruptions occur during the examination of an eye, which interruptions are caused by the mechanical design of an eye, which interruptions are caused by the mechanical design of the Scheimpflug camera.
The basic purpose of the invention is therefore to provide a device for the examination of an eye, with which without interruptions and returns to an initial point the eye can be multiply scanned.
This purpose is attained according to the invention by the slit light projector and the Scheimpflug camera being freely rotatable about the axis for more than 360.degree., and by a voltage supply to both the Scheimpflug camera and the slit light projector occurring through a transmitter.
A wireless connection to the voltage supply, the Scheimpflug camera and/or the slit light projector is made possible by the transmitter of the invention. The angle of rotation of the Scheimpflug camera and of the slit light projector is therefore no longer limited by cable. By multiple rotations of the slit light projector and of the Scheimpflug camera the eye can thus be scanned in a quick sequence and the slit images can be photographed.
The transmitter is according to the invention a sliding ring transmitter. The Scheimpflug camera and the slit light projector are advantageously mounted on a rotor rotatably supported on the stand, whereby the axis of rotation of the rotor is the optic axis of the slit projector. According to the invention it is then possible to mount a computer unit on the rotor, which computer unit is connected to the scheimpflug camera.
According to the invention a wireless data transfer path can exist to the Scheimpflug camera and/or the computer unit. This wireless data transfer path can advantageously be guided over the sliding ring transmitter. Just like the voltage supply by means of a transmitter, the wireless data transfer path is suited for the Scheimpflug camera with the slit light projector being able to be rotatable through any desired angle. Due to the fact that a computer unit is already installed on the rotor, a large portion of the needed data processing of the image data delivered by the Scheimpflug camera can already take place in said computer. In particular when, as it is particularly advantageous, a CCD-camera or C-MOS-camera is used, the digital signal of the computer unit, which signal is delivered by these cameras, can be converted into an analogous signal, with the result that only two electric signals must be guided through the transmitter instead of the 16 signals common for a digital coding.
The stand of a Scheimpflug camera of the invention can be advantageously moved about three orthogonal axes.
The slit light projector has in a particular embodiment of the Scheimpflug camera a light source, a slit diaphragm arranged in front of the light source, and a lens system arranged in front of the slit diaphragm. The light source consists thereby of several illuminating diodes arranged side-by-side and essentially in longitudinal direction of the slit, namely in the plane of the projected slit.
The inventive use of illuminating diodes as a light source in the Scheimpflug camera has many advantages. The most important advantage for the ophthalmologist is the high speed, with which the flashes needed for slit image photography can be produced with the illuminating diodes. Moreover, illuminating diodes are significantly compacter than the common light sources; the illuminating diodes are more robust than, for example, highly sensitive Xenon-high-pressure lamps and noticeably less expensive.
The illuminating diodes of the Scheimpflug camera can according to the invention be arranged arc-shaped or circularly in this special design. The curvature of the arc is then advantageously determined such that an as large as possible amount of light passes through the lens system. However, it is also possible that in the special design of the Scheimpflug camera the illuminating diodes are arranged essentially in a plane parallel to the slit diaphragm. The main beams of the illuminating diodes are then advantageously inclined relative to the optic axis of the lens system, and the inclination of the main beams corresponds with the distance of the illuminating diodes from the optic axis. The main beams intersect advantageously in one common point of intersection.
The slit light projector can in the special design of the inventive scheimpflug camera have advantageously a second slit diaphragm in front of the lens system, whereby the slit of this second slit diaphragm is coaxial and aligned with the slit of the first slit diaphragm.
The illuminating fields of the illuminating diodes can according to the invention consist of illuminating diode chips. These illuminating diode chips are then advantageously arranged along a straight line, whereby the connecting fields lie on both sides of the straight line. With this arrangement of the illuminating diode chips it is achieved that the areas of the illuminating diode chips, which areas are uncovered by the connected fields, lie as much as possible at the edge of the illuminating fields reproduced on the first slit diaphragm, and an as large as possible amount of light reaches the lens system.
The diode lenses can according to the invention be astigmatic and/or the lens system can consist of cylinder lenses. A concentration of the light produced by the illuminating fields on the slit in the first slit diaphragm is achieved in both cases.
The first slit diaphragm can according to the invention have a width of 50 to 120 .mu.m, whereas the aperture angle of the concentration of beams exiting from this first slit diaphragm is not supposed to be larger than 2.9.degree.. In order to obtain an advantageous scattering behavior, illuminating diodes, which produce a blue light, are preferred.